The mask appears a lot smaller on the chathead than on the character him/herself. The chathead version overlaps the face, but on the actual character model, the mask falls just past the character's chest.

The Lumbridge sage appears to have a blue tribal mask on his rug of items next to him.

If you talk to any of the villagers in Tai Bwo Wannai while wearing the mask, they'll be scared thinking you're a broodoo victim coming to kill them.